Answer found in the Dell P2414H User’s Guide. Use the monitor OSD (On Screen Display) - Input Source Select to change the source. But you need to first explain what video out port the computer and TV have to connect to the P2414H DP/DVI/VGA video in ports.

thank you  chris-the computer i connect to the monitor with  a dvi-d cable [every thing is ok] the tv  converter has only  hdmi out put . i connect it to the monitor with  a dp to hdmi cable i use the osd and the monitor did not recognized this connection, 

TV HDMI out cannot upconvert to the monitor DP via a straight cable. You need to find some HDMI to VGA converter.

TV HDMI out --> HDMI to VGA converter --> VGA to VGA cable --> Monitor VGA in

thanks  you- if i connect .....

hdmi [tv converter ]  to the dmi  monitor [i have a cable]     

      and     vega computer to vega monitor 

do you think it can be good

how can i connect two sources to one monitor [p2414h]  and change between them .

If the sources have HDMI outputs, I suggest an HDMI switcher.